Low-dropout regulators (LDOs) are known in the art. FIG. 1 schematically illustrates such conventional LDO. Broadly speaking, the LDO of FIG. 1 consists of an error amplifier input stage, a common source second stage, which converts the error signal into a current, and a current mirror to amplify said current in a predetermined ratio to be supplied to the output load. In more detail, the LDO comprises an input terminal 10 to which an input voltage is applied, and output terminal 20 at which a regulated output voltage is output, an error amplifier 40 receiving a reference voltage and a predetermined fraction of the output voltage at its input terminals, a switching element 45 that is controlled by the error amplifier 40, and a current mirror 30, 35 for mirroring a current flowing through the switching element 45 to the output terminal side to be supplied to a load connected to the output terminal 20.
A threshold voltage for the input voltage above which the output voltage is regulated by the LDO depends on the predetermined fraction of the output voltage that is applied to the error amplifier 40, and on the reference voltage. For input voltages below the threshold voltage, the LDO is in the dropout mode (dropout condition) and the output voltage is not regulated. In this case, the switching element 45 is fully open, and the current I_diode flowing through the switching element 45 is only limited by the on-state resistance of the switching element 45 and the diode voltage drop of the transistor 30 on the input side of the current mirror (i.e. the transistor of the current mirror conducting the input current). Accordingly, the quiescent current of the conventional LDO described above is comparably large, resulting in undesirably large current consumption of the LDO, even for small load currents.